When I was looking up how to add meta data in Dreamweaver I found a couple of Web sites that professed to not finding any way to do it. This isn't terribly surprising to me, because it's very hard to find. But when you realize where it is, the location makes sense, you just have to be willing to look for it.
Go to the "Insert" menu. From there, choose "HTML" and from there choose "Head Tags". This gives you the option to edit keywords, description, add a meta refresh, a base URL or link to an external document like a style sheet. You can also add any other meta tag you know of by choosing the "Meta" option.